A fiber optic gyroscope (FOG) is an instrument used to measure angular rotation. Unlike conventional gyroscopes, a FOG has no mechanical moving parts. This feature gives a FOG several advantages over conventional gyroscopes. For example, a conventional gyroscope must get the gryo rotor spinning up to speed before it can provide readings whereas a FOG is always ready to give immediate readings. Additionally, unlike conventional gyroscopes, a FOG is less sensitive to g-forces. These advantages make a FOG especially suited for high performance applications such as satellites, submarines, strategic missiles, and pointing and stabilizations applications among others. As a result, FOGs are widely used in defense and commercial applications.
A typical FOG operates by passing light from a fiber light source through a beamsplitter where it is divided into two light waves with the same intensity. These two light waves then enter a fiber coil. One light wave will travel in a clockwise direction and the other in a counter-clockwise direction. The two light waves will join again as they leave the coil. If there is no rotation, the two light waves will travel equal optical path lengths and be in phase when they join, creating constructive interference. If there is rotation, the effective optical path length that the light waves travel will change and the two light waves will be out of phase when they join, creating destructive interference. The magnitude of the shift in phase is proportional to the rate of rotation and the interference intensity which is used to measure rotation. Current FOG random noise performance is limited by both the relative intensity noise (RIN), which is inversely proportional to the optical linewidth, and the output power of the fiber light source. Additionally, the gyro bias errors due to polarization cross coupling, Rayleigh back scattering and nonlinear Kerr effects can be significantly reduced by using a low RIN light source. Accordingly, it is desired to have a fiber light source with an ultra-low RIN (very broad optical linewidth) and high power to increase the performance of FOG systems.
For the reasons stated above and for the other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an improved fiber light source.